Process for activating catalysts



. 'Iv'his invention relates to the;,;a ctivation of t r -ta il a y is 1ii b v for t e 'd r o. l hur rier-ice. 7

George florsley, Norton c n 'ilees, 1 land, .assign'or tolmperialphemical Industries V L imite d,a corporation .ofVGreat Britain f NoDrawirig; Application May 8,-1944,'-Sei'ialNo. .g a i 53451694; r'l'n Great BritainfApril 29, 1943 a: i; Y

il i l f il i (cum-239)" l catalyst .can occur for example due-to expos'ure to excessively hightemperatures resulting from f e il anoperation of the plantkorf due to poisong 7 mg, for example by compounds of arsenic. 7 Also the initial;v activity of platinum containing vcate alysts may be low due to faulty preparationsand andl g v 3 JIIhe present inventionfprovides a; process whereby notkonly can -{deactivated platinum containing catalysts be reactivated but by means of which the activity of eatalysts prepared by' wa aama a. activity can'b improve v v 7 According to the present invention platinum cqnia naq t is suitab e mim -o at o o sulphur dioxideto sulphur, trioxide j are activated by tr a me wi h -a zasi ie s;s u i ob d by -theinteractionoi sulphur dioxide and metallic iron in the presence qi -waterl; V The; aqueous; -solution -suitable for use; accordii-sit? ther e mve on may br r by placing water and metallic iron, for example;

nd having normal or J poor in thef'form of iron'nailsfin a suitable container an ljrna a o sv sulphur x der q-t e tiu az After .c iQ p h eam o su ur d 'Q fi rhe aqueous ion; may beiideca te from residual metallic iron before use.; Alternativelyxi e metallic ironmay be; treated with a squea s o u n o su phur; diexida u n the prep ration of, thesolutions. it islodesirabl e tokeepivth'em cool, that is at a temperature. not

above 20" 'C. and. preferably in the region of C. I norder to obtain the maximum increase in the activity'of a given 'catalyst, theis'olution should be used as soonas possible after its preparation,

and kept 0001 during the reactivation treatment.

7 tion. Alternatively, the metallic; iron emay -loe cool,- for example, ;at, a; temperature not above 20."':C:':and preferably near 0? G.

If desired direct contact between the metallic iron and the catalystm'aybe avoided for example by placingtheemetallic iron: in a suitable vessel and separated :froin -.the acatalyst to 1 be activated by'me'an's ofga' partition through. which liquid can' passt for-example, the partitiommay be'constructed of gauze; perforatedplate;porous earthenware or refractory material.- It should be" understood that such materials should be sub-l 'stantially inert under .the conditions of reactiva placed (in a container .throug'hjthe rwallszotfwhich liquid can pass; thiscontainer; then being placed in'a-vessel containing the catalyst. In both cases an aqueous solution of sulphur; dioxide;v may-then be.=:;introduced into/the vessel, or. waterzpmaywbe placed'zindt :and gaseous sulphur dioxide passed through'." :r m As"a.=further feature .of the present invention, it has been found that even -'b.etter activation can be obtained; if. the-catalyst. is: given a preliminary treatment withknitrichcid. ;A dilute solution, for example, one containing 10% by weight of nitrie acid, is satisfactory. The nitric acid may be used warms The preliminary treatmeat-"may be followed 'bya washing of the catalyst with water before the treatment with the aqueous" solution obtained by the interaction of sulphur'fdioxide and metallic iron in the presence of water; Thetreatment'with the aqueous solu ti'on obtaine'd by the interaction" of sulphur di'-' oxide and metallic iron in the presence of water with or 'without 'a preliminary treatment with nitric 'acidymay be repeated one or more times;

We have foundthe process 'of'this invention particularly suitab1e -for the treatment of cat- After treatment with the solution'and separa with water and dried by: cautious l-heating.v 1 v Instead .offpreparing' the activating solution separately and using-itas hereinbefore described, it has beencfoundpreferable topproduce the so1ution; in situt, Thus the metallic iron may b e mixed-with the catalyst to be activated and the mixture treated with anaqueous solution cong. sulphur 1 dioxide or. with gas'eous sulphur H w Water $6 he m1,

During suchalysts containing platinum supported-vonwsilica v gel, l

tion from any residual iron the catalyst is washed I temple 2 TESA': (lament mantecbnj tairimg 6%1193? vol umeof sulphur dioxide and"94 by vo'1 ume;.;of was passed at arate of .1Q0 litres perhour over :43. gins. of a deactivated silica gjel catalyst containing-.QL8% by weight of platinum, the inlet gas temperature being maintained at 330; C, The. conversion of sulphur dioxide to sulphur trioxide was found to be 72.7 .Q I

Compared with this asample of the same deg activatedi catalyst was, mixed/with iron nails and t" id with ra e -a e us Sol io c di e, @139. nu es at mo Example 2 v V A sample of the same deactivatedcatalystas" used in Example 1 was digested for 50 minutes in a cold nitric acid solution containing by m weight of nitric acid, washed-with water; mixed;.-

with iron nails and treated with a saturated aqueous solution of sulphur dioxide for 30 mmutes at room temperature. After washing-with water, removing the iron nails and drying as above described, the catalystwaseused:under the:

same conditions as in Example 1 Whenthe; cone version of sulphur dioxide to sulphur trioxide was found to be 88%.

By repeating the treatment used in this example, it was found that aconversion of sulphur dioxide to sulphur trioxideof; 92% wasobtained;

Example. 3 p V A dry gaseous mixture containing 6% byvolume of sulphur dioxide and. 94% by volume. of air was-passed over: a silica gel catalyst containing 0.3% by weight. of platinum at a rate; of 100 litres per hour per 36 gms the inlet gas temperature being maintainedat 380 C. Theconversion ofsulphur dioxide to sulphur trioxide.Was;-;62% After activation of this: catalyst: as described in Example 1, thesconversion roseto 82%.

Hydro-gen containing a little arsinewas; then passed over the catalystwhich.wasrmaintained at: 4003-02, after which-the? catalyst was used for the productionxof' sulphur 'trioxide underthesame conditions asbefore the poisoning with arsenic. It was then vfound thatthe conversion: had fallen to 76%. After reactivation under the same conditions as in'Example 1, the catalystrwasagain used forthe conversionsof sulphur'dioxidea to sulphur trioxide, as" above described.

The conversion was found to be 82%. I

Example 4f A drygaseous, mixture containing 6% by volume ofsulphu-r" dioxide andv 94% by volume of air waspassed' at a rate of 100' litres-per hour over by'weight of platinum, the'inletgasvtemperature beingmaintained at: 390 C. The conversion of sulphur dioxide: to sulphur trioxide was found tovbe:67 %.w-- w After treating the catalystv once as described in-Example'2; theconversion under-the sameqconr- U used in Example 4 was. treated as, follows.

4 washed in running water for 10 minutes, and afterwards dried.

After thi treatment the catalyst was tested under the same conditions as in Example 4 and the conversion of sulphur dioxide to sulphur trioxide was found to be 87%.

Ifcla imfl-y a g f j I.'"A process for the'activation of platinumcontaining catalysts suitable for the oxidation of sulphur dioxide to sulphur trioxide comprising treating; the-catalyst with an aqueous solution prepared by the interaction of sulphur dioxide and metallic iron in the presence of water. 2; A processxforthe activation of platinumcontaining catalysts suitable for the oxidation of sulphur dioxidev to sulphur trioxide comprising interactingi-sulphur dioxide and metallic iron in the presence of water, removing residual iron from the solution and treating the catalyst with The catalyst was digested for 30""minutes' in i.

cold 10% nitricacid', and then washed in run ning water' for 10min'utes. Meanwhile; sulphur dioxide was passed "into ice-water" to which iron nails had been added thetemperature-beingmaintained at about 5 C. by means'of ice. The orange coloured solutionwas' decanted from theiron the solution. y

3, A process for the activation of platinumcontain-ing catalysts s'uitable f'ortheox'idationof sulphur dioxide to sulphur trioxide which 'com-' prises interacting sulphur dioxide and metallic iron' in the presence of water and the catalyst.

4. vA process for the activaticn of platinum-' containing catalysts suitable for'the oxidation of sulphur dioxide to sulphur triox-ide which comprisesi'nteracting sulphur dioxide and metallicv ironin the presence of water-=at atemperature not exceeding 20 C.', separating; residual iron from the solution and-treati'ngthe catalyst'with' the-solution.

5. 'A process for the activation of platinum containing catalysts suitable for the oxidation of sulphurdioxide to sulphur tri-oxide comprising treating the catalystat a'temperature notexceeding 20 C. with an aqueous solution prepared by the interaction of sulphurdioxide and metalliciron in the presence of wateri p 6'.- A process for the activation of platinumcontaining catalysts suitable forthe oxidationof sulphurdioxide'to sulphur trioxide comprising; interacting sulp-hur dioxide and metallic iron in the presence of water and the catalyst at a temperature not exceeding-20 C.

' 71A process for the activation of platinumcontairiingcatalysts suitable for the oxidationof- 36 ems; of a silica gel catalyst containing; 0.3% sulphur d'ls'xlde sulphur de-comprrsmg} sulphur dioxide to" sulphur trioxide comprising treating vthe catalyst with nitric acid, washing with. Water, and;then treating the catalyst with aiilaqueoussolution prepared by the interaction ofvv sulphur dioxide and metalliciron in the pres-' encev of water at: a temperature" noteexceedingl 20 C. I

9: 'A; process: for; the-"activation; of platinum containing catalysts suitable for: the oxidation of sulphur: dioxide to sulphur? trioxide comprising treatin'g tlie catalyst with aniaqueous; solution obtained by the interaction of sulphur dioxide: andjrnetalli'c iron in the presence ofwater at-a temperature in'the region-of0C. I Y

10.. A process for; the activation of platinumcontaining catalysts suitable for the oxidation of sulphur dioxide to sulphur" trioxide comprising interacting sulphur dioxide and metallic iron in with water and. then treating the catalyst at a temperature in the region of 0 C. with an aqueous solution obtained by the interaction of sulphur dioxide and metallic iron in the presence of 5 water at a temperature in the region of 0 C.

GEORGE FREDERICK HORSLEY. 

